A similar method is described by O. Niwa et al. in Makromol. Chem., Rapid Commun. 6, No. 6, 1985, pp. 375-379. According to the method described therein, an insulating polymeric base film has been applied to an anode, which is placed in an electrolyte solution also containing pyrrole. As a result of an applied voltage, the pyrrole monomers diffuse from the electrolyte solution to the base film, where they polymerise to form polypyrrole. In this way, a film with electrically conductive properties is obtained. The pyrrole monomers polymerise both on and within the base film.
The method described by O. Niwa et al. is suitable for the preparation of a polymeric shaped article with electrically conducting properties. The method of Niwa has the disadvantage of being uneconomically low in productivity. Firstly, only a relatively small piece of base film, essentially having the same size as the anode, can be applied at a time. Further, the application of the base film onto the anode is time-consuming since a very intimate contact over the whole of the surface is required. Then the process of making the film conductive is dominated by the intrinsically slow diffusion of the pyrrole through the film and finally the conductive film has to be peeled off from the anode on the risk of damaging the film, that tends to stick to the anode.
A further disadvantage is that the base shaped article applied by Niwa swells in the electrolyte solution, so causing the mechanical properties of the base shaped article to deteriorate and making the film stick to the anode. Another added disadvantage of the base shaped article applied by Niwa is that a high voltage needs to be applied in order to realise a short polymerisation time or a high rate of production.